Locking device

ABSTRACT

The invention concerns a clamping device for a device for the production of metal parts by forming with a closed forming tool, the clamping device comprising at least 
         several tension hoops ( 2 ), these tension hoops ( 2 ) each being provided with at least one tension frame ( 2.2 ) of a closed contour, the tension frame being provided with two segments ( 2.3 ) arranged opposite each other at some distance, between which a forming tool ( 12 ) can be arranged, each of these segments ( 2.3 ) being provided with at least either one bearing surface ( 2.1 ) or one bearing surface ( 2.4 ), and the tension hoops ( 2 ) being each linked by at least one articulated joint ( 8 ) in order to be pivoted,    a bearing surface ( 3.1 ) which is located above or on the upper surface of the forming tool ( 12 ) and used as support for a bearing surface ( 2.1 ) of a tension hoop ( 2 ), and    a device ( 5 ) which generates a clamping force of more than 3 MN and is composed of several power-generating elements.

The invention concerns a clamping device for a device for the productionof metal parts by forming with a closed metal forming tool as well as adevice for the production of metal parts by forming with a closedforming tool which is provided with the clamping device specified in theinvention. The invention also concerns a structural component for aclamping tool of a device for the production of metal parts by formingwith a closed forming tool.

As used in the invention, the designation of “metal forming with aclosed forming tool” defines all metal forming procedures during whichthe application of a force to the workpiece to be formed occurs inside aforming tool which is essentially composed of several parts but which issubstantially closed at the moment of the application of the force, andduring which the forces to lock the forming tool are regularly higherthan 3 MN, an example of such a forming procedure being the so-calledhydroforming process using forming tools which are parted in alongitudinal direction.

In hydroforming processes, the devices used will generally be powered byhydraulic systems. The arrangement of such devices is largely determinedby the workpiece to be produced, and the original forming body willalways be a tube-shaped hollow body. The main cylinders used for powertransmission to the tube extremities will be arranged either in anupright or a horizontal position so that they act in opposite directionsin the direction of the initial tube axis. One of these cylinders willgenerally be provided with a hollow bore and a high pressure connectionwhich is generally connected to the pressure intensifier by means of apipe joint.

The forming tool has at least two components. In the simplest scenarioof a two-part forming tool, one tool component is secured to the machinetable, whilst the other is powered and performs an opening and closingmotion as defined by the working cycles. Depending on the desiredworkpiece geometry, the devices can optionally take up forming toolswhich are either parted in the longitudinal or cross direction; whereclamping forces of more than 3 MN will generally require forming toolswhich are parted in a longitudinal direction. Mostly, those devices willonly be of economic value where higher numbers of pieces are produced,that is especially where short working cycles are used.

In many cases, the devices for hydroforming processes which are providedwith a forming tool which is parted in the longitudinal direction downthe tube axis are designed as multicolumn presses or frame presses. Theforming tool is mounted so that the plunger of the press moves onecomponent of the forming tool up during tool change. During the formingprocess, the plunger should compensate the force resulting from theworkpiece surface area projected and the interior pressure and apply aforce of at least the same value or higher to the forming tool. Due tothe high interior pressures used in the process (generally more than1000 bar), the clamping forces required in this respect which are higherthan 3 MN must be ensured by the steel structure of the device, whichwill require relatively high constructional heights and much space forassembly and operating purposes when using multicolumn presses or framepresses. The device will involve costly foundation work and large spacerequirements where the forces to be absorbed are 3 MN or higher and thedead mass generally resulting from such structures is accordingly high.Any tool change, including that of the forming tool, will be subject tohigh technological expenditure.

The publication DE 1 602 475 B2 describes a pressing device for theproduction of hollow workpieces constructed of sheet metal underinterior hydraulic pressure by cold forming processes where the moveableparts of the parted mould encompassing the workpiece are locked togetherby means of pivotable clamping hooks during cold forming. Where such apressing device is required to ensure clamping forces of more than 1 MN,in particular more than 3 MN, the clamping mechanism, in particular theclamping hooks or joints which are needed for the pivoting motion of theclamping hooks, must be sufficiently dimensioned. Such devices of a deadmass of several metric tons must be based on expensive foundations andwill have large overall construction heights. The clamping hooks, as faras they are able to guarantee the required clamping forces in the firstplace, can only be operated with heavy forces and high energy.

The short cycle times of between 20 and 40 seconds which are an economicnecessity for a profitable operating of the device within industrialmanufacturing processes, are not realistic in view of the high momentsof inertia occurring. This solution will result in the formation of gapsbetween the components of the forming tool produced during the formingprocess proper, which mainly results from the elastic deformation of thematerial used for the clamping hooks, and which will lead to anundesired deformation of the workpiece during power build-up.

It is the aim of the invention to provide both a device and a componentof such a device which have a lower construction height and a low deadmass and will require a lower expenditure regarding the amounts ofinvestment, maintenance and operation and can be operated in aneconomical way and which are not subject to forming gaps between thecomponents of the forming tool during forming.

The requirement of the invention is met because the clamping deviceaccording to the invention comprises at least:

-   -   several tension hoops 2, these tension hoops 2 each being        provided with a tension frame 2.2 of a closed contour, the        tension frame being provided with two segments 2.3 arranged        opposite each other at some distance, between which a forming        tool 12 can be arranged, each of these segments 2.3 being        provided with at least either one bearing surface 2.1 or one        bearing surface 2.4, and the tension hoops 2 being each linked        by at least one articulated joint 8 in order to be pivoted, the        material of the tension frame 2.2 mainly consisting of materials        of tensile strengths between 1500 N/mm² and 4200 N/mm², an        endurance strength of between 1200 N/mm² and 3000 N/mm² and a        density of between 1.2 and 2.5 g/cm³,    -   a bearing surface 3.1 which is arranged above or on the upper        surface of forming tool 12 and is used as support for a bearing        surface 2.1 of a tension hoop 2, and    -   a device 5 which produces a clamping force of more than 3 MN and        is composed of several power-generating elements, the clamping        force being applied between the bearing surfaces 2.1 and 2.4 of        the tension hoops 2 and at least one surface area located        beneath forming tool 12.

The selection of materials of the invention and the constructionaldesign of the material will, on the one hand, allow for a technicallyeasy pivoting of the tension hoops using a low amount of energy in orderto obtain reasonable cycle times, and, on the other, result in theoccurring of a low amount of dynamic forces.

The fact that the invention makes use of and selects materials asconstruction materials, the properties of which are described in thefirst patent claim, makes way for new constructive solutions and/or newmachine designs, as compared to the materials used in forming technologyup to date, including structural steel.

The tensile strength of a carbon fiber compound is, for instance, ofapprox. 2950 N/mm² (structural steel of approx. between 320 and 690N/mm²), the endurance strength of approx. 1950 N/mm² (structural steelof approx. 350 N/mm²), and the density of approx. 1.8 g/cm³).

By designing the element of clamping mechanism as a tension hoop whichwill provide the required clamping force the invention makes apurposeful use of the improved material properties of the materialspreferred in the invention, such as carbon fiber compounds, whichresults in the proportion between the strength of the design and thetension frame mass being 800, for instance.

The depending Patent claims 2 to 8 indicate advantageous furtherdevelopments and improvements of the clamping device under theinvention.

The requirements of the invention are furthermore met by a device forthe production of metal parts by hydroforming which comprises at leastone parted forming tool and a device as described under Patent claims 1to 8.

The requirements of the invention are furthermore met by a structuralcomponent for a clamping tool of a device for the production of metalparts by hydroforming where a closed forming tool as described underPatent claims 10 is used.

The depending Patent claim 11 describes advantageous developments andimprovements of the structural component as described in the invention.

The drawing shows an example of the design of the invention which isspecified in detail in the description below.

It includes:

FIG. 1 a Side view of a clamping device

FIG. 1 b Another side view of a clamping device as in FIG. 1 a

FIG. 2 a Perspective view of an alternative scenario of the clampingdevice with a closed forming tool

FIG. 2 b Perspective view of a clamping device with an opened formingtool

FIG. 3 a Side view of a component part for a clamping device

FIG. 3 b Another side view of component part for a clamping device as inFIG. 3 a

FIG. 1 shows a side view of a clamping device 1 under the inventionwhich is a constituent part of a device for the production of metalparts by hydroforming which contains a two-part forming tool 12. Amachine base 6 is secured on a foundation 13, the machine basesubstantially consisting of a box-shaped structural steel construction.A frame 6.3 is bolted down to another frame 6.1 by means of a column6.2. The column 6.2 is provided with two articulated joints 8 which arerigidly mounted in the direction of the longitudinal axis of the machinebase 6. The two tension hoops 2 are so linked to the articulated joints8 that these tension hoops 2 can be pivoted in an almost parallel way tothe longitudinal axis of the machine base 6. Two hydraulic pivotingcylinders 9 which are located on the frame 6.3 activate the pivotingmotion of the tension hoops 2. The four corners of frame 6.3 areprovided with four lifting cylinders 4 which rest on the frame 6.3 andare connected to crossbeam 3.

Crossbeam 3 is provided with plane bearing surfaces 3.1 on which theequally plane bearing surfaces 2.1 belonging to tension hoops 2 whichare arranged parallel to those can rest when they are positioned. Theupper part of the two-part parted-in-length forming tool 12 is mountedto the Crossbeam 3. The lower part of the forming tool 12 is bolted downto machine table 7. The machine table 7 loosely sits on the pistonbearing surfaces of the four pressing cylinders which constitute thepower-generating elements of device 5.

The pressing cylinders are mounted to the frame 6.1 so that thesepower-generating elements of device 5 acting on the same tension hoop 2,preferably comprising several hydraulic high-pressure cylinders, arearranged so that the central power-applying lines generated by thesepower-generating elements of device 5 run almost parallel and along aplane which is not substantially different from the plane separating thetension hoop 2 in an axial direction. The segments 2.3 are largelyconstructed from some light metal material, such as aluminium alloys.The tension frames 2.2 mainly consist of a carbon fibre compound, e.g.an intermodular fiber of a volume portion of fibres of approx. 50/65% inan epoxy resin matrix.

The functional sequence of the above device is described in its contextin the following.

After placing the workpiece into the opened forming tool 12, the latteris closed by lowering the pistons of lifting cylinders 4 until bothparts of forming tool 12 come to rest. The pivoting cylinders 9 are nowused to pivot the two tension hoops 2 to the vertical condition in orderto create a gap which is necessary to allow a contact-free positioningof tension hoops 2, the gap being located between the bearing surfaces3.1 of crossbeam 3 and the bearing surfaces 2.1 of the tension hoops 2.The pressing cylinders are now used to apply clamping forces on toforming tool 12 along machine table 7. The machine table 7 and the wholeforming tool 12 are now lifted until the contact is made between thebearing surfaces of crossbeam 3 and the tension hoops 2. Both parts ofthe forming tool 12 are then subjected to the required clamping force,which results in the forming tool 12 being clamped.

FIG. 2 shows an alternative scenario of the clamping device with theopened die in a perspective view (FIG. 2 a and/or FIG. 2 b). The machinebase 6 mainly consists of a box-shaped steel construction. A bottomframe 6.3 is bolted down to another frame 6.1 by means of fourvertically arranged beams. A tension hoop beam 10 which is connectedwith four spring guides 11 to the frame 6.3 is mounted between these twoframes. The two articulated joints 8 are mounted to tension hoop beam10. The articulated joints 8 are provided with the two tension hoops 2which are linked to their lower ends in order to enable these to pivotparallel to the longitudinal axis of the machine base 6. Two hydraulicpivoting cylinders 9 which are located on frame 6.3 are used for thepivoting of the tension hoops 2. The four corners of frame 6.1 areprovided with four vertically arranged lifting cylinders 4 which areconnected to crossbeam 3. Crossbeam 3 is provided with plane bearingsurfaces 3.1 on which the equally plane bearing surfaces 2.1 arrangedparallel to those of tension hoops 2 can rest when they have beenpositioned (FIG. 2 a). The two tension hoops 2 each consist of twosemicircular segments 2.3 arranged opposite each other, the almostsemicircular contours of the upper and lower segment 2.3 each facingdifferent directions. The annular rigid tension hoop 2.2 wraps aroundthe semicircular contours of the upper and lower segment 2.3 and isconnected to these. The upper part of the two-part forming tool 12 isfixed to crossbeam 3. The lower part of the forming tool 12 is bolteddown to frame 6.1 to the base of which the four pressing cylinders 5protruding downwards are mounted. The pressing cylinders 5 will movethrough the four openings of the tension hoop beam 10 and press down onthe bearing surfaces 2.4 of the lower segments 2.3 (?). The pressingcylinders are mounted to the frame 6.1 so that the centralpower-applying lines generated by these power-generating elements ofdevice 5 run almost parallel and along a plane which is notsubstantially different from the plane parting the tension hoop 2 in anaxial centerline direction when tension hoop 2 is positioned (FIG. 2 a).

The functional sequence of the above device is described in its contextin the following:

After placing the workpiece into the opened forming tool 12, the latteris closed by lowering the lifting cylinders 4 until both parts offorming tool 12 come to rest. The pivoting cylinders 9 are now used topivot the two tension hoops 2 to their vertical position in order tocreate a gap which is necessary to allow a contact-free positioning oftension hoops 2, the gap being located between the bearing surfaces 3.1of crossbeam 3 and the bearing surfaces 2.1 of the tension hoops 2. Thepressing cylinders are now used to apply forces on to the bearingsurfaces 2.4 of the tension hoops 2. Tension hoop 2 is lowered until thebearing surfaces 3.1; 2.1 of the crossbeam 3 and the tension hoop 2 comeinto contact. The required clamping force which is applied by thepressing cylinders is now applied so that the forming tool 12 is clampedwith the help of these clamping forces and the parts of forming tool 12can no longer open during the forming process.

FIG. 3 contains a side view of a component part for a clamping tool 1 asa constituent part of a device for the production of metal parts byhydroforming which is provided with a two-part forming tool 12. Amachine base 6 is bolted down to a foundation 13, the machine basemainly consisting of a box-shaped construction made of structural steel.A frame 6.3 is bolted down to another frame 6.1 by means of a column6.2. The column 6.2 is provided with two articulated joints 8 which arerigidly mounted in the direction of the longitudinal axis of the machinebase 6. The two tension hoops 2 and therefore a pair of the designstructure described in the invention are linked to the articulatedjoints 8 in a manner that these tension hoops 2 can be pivoted in aalmost parallel way to the longitudinal axis of the machine base 6.

As an alternative scenario which is not described in FIG. 3 the tensionhoop 2 can be located so that it can be axially shifted towards tool 12.

Two hydraulic pivoting cylinders 9 which are mounted to the frame 6.3are used to activate the pivoting motion of the tension hoops 2. Thefour corners of frame 6.3 are provided with four lifting cylinders 4which rest on the frame 6.3 and are connected to crossbeam 3. Crossbeam3 is provided with plane bearing surfaces 3.1 on which the equally planebearing surfaces 2.1 belonging to tension hoops 2 which are arrangedparallel to those can rest when they have been positioned. The upperpart of the two-part parted-in-length forming tool 12 is mounted to theCrossbeam 3. The lower part of the forming tool 12 is bolted down tomachine table 7. The machine table 7 loosely sits on the piston bearingsurfaces of the four pressing cylinders which constitute thepower-generating elements of device 5. The pressing cylinders aremounted to the frame 6.1 in such a way that these power-generatingelements of device 5, preferably several hydraulic high-pressurecylinders, acting on the same tension hoop 2 are arranged so that theclamping force or the clamping forces act on the tension hoop 2 in sucha way that the net force of the power-applying lines runs almostparallel and along a plane which is not substantially different from theplane parting the tension hoop 2 in a centerline axial direction. Thesegments 2.3 are largely constructed from some light metal material,such as aluminium alloys. The tension frames 2.2 mainly consist of anonmetal compound material with embedded reinforcements, here of acarbon fibre compound, e.g. an intermodular fiber of a volume portion offibres of approx. 50/65% in an epoxy resin matrix.

The functional sequence of the above device is described in its contextin the following:

After placing the workpiece into the opened forming tool 12, the latteris closed by lowering the lifting cylinders 4 until both parts offorming tool 12 come to rest. The pivoting cylinders 9 are now used topivot the two tension hoops 2 to their vertical position in order tocreate a gap which is necessary to allow a contact-free positioning oftension hoops 2, the gap being located between the bearing surfaces 3.1of crossbeam 3 and the bearing surfaces 2.1 of the tension hoops 2. Thepressing cylinders are now used to apply the clamping forces on to theforming tool 12 along the machine table 7. The machine table 7 and thewhole forming tool 12 are lifted until the contact is made between thebearing surfaces of crossbeam 3 and the tension hoops 2. Both parts ofthe forming tool 12 are now subjected to the required clamping force,which results in the forming tool 12 being clamped.

The component part described in the invention can also be used as anintegral element of a clamping tool for the forming or interior formingof plastic, metal, ceramic or glass parts.

The workpiece can be formed inside by blow moulding or injectionmoulding of larger plastic parts, for instance. The structural unitdescribed in the invention, provided with one or several componentsdescribed in the invention, could be used for the gap-free closing of atwo-part blow mould. The principle of the invention can easily betransferred by a specialist engineer according to known procedures afterhaving adjusted the usual parameters.

A further example for the use of the invention due to its principle isoffered by the casting of metal, ceramic or glass parts according toknown procedures.

1-12. (canceled)
 13. A clamping device for a closed forming tool,comprising: a plurality of tension loops each having at least onetension frame with a closed contour, said tension frame having twomutually opposite segments each formed with at least one bearing surfaceand spaced apart at a spacing distance for receiving a forming tooltherebetween, said tension loops being pivotally disposed about at leastone articulated joint, and a material of said tension frame primarilyconsisting of a reinforced compound; a bearing surface disposed above oron an upper surface of the forming tool for supporting said bearingsurface of a respective said tension loop; and a device for generating aclamping force of more than 3 MN, said device including a plurality offorce-generating elements, and wherein the clamping force is appliedbetween said bearing surface of each said tension loop and at least onesurface area beneath the forming tool.
 14. The clamping device accordingto claim 13, wherein the material of said tension frame primarilyconsists of materials having a tensile strength between 1500 N/mm² and4200 N/mm², an endurance strength of between 1200 N/mm² and 3000 N/mm²and a density of between 1.2 g/cm³ and 2.5 g/cm³.
 15. The clampingdevice according to claim 13, wherein said device for generating theclamping force is disposed between said bearing surfaces of said tensionloops and directly on the forming tool.
 16. The clamping deviceaccording to claim 13, wherein the device for generating the clampingforce is located between said bearing surfaces of said tension loops andindirectly on the forming tool.
 17. The clamping device according toclaim 13, wherein said force-generating elements of the device on thesame tension loop being arranged so that the central force-applyinglines of said power-generating elements of the device run substantiallyparallel and along a plane that is not substantially different from aplane parting said tension loop along a centerline axial direction. 18.The clamping device according to claim 17, wherein said force-generatingelements of the device are one or a plurality of hydraulic high-pressurecylinders.
 19. The clamping device according to claim 13, wherein atleast one of said tension loops is movably disposed to shift towards theforming tool in an axial direction.
 20. The clamping device according toclaim 13, wherein said tension frame consists essentially of a nonmetalcompound material with embedded reinforcements.
 21. The clamping deviceaccording to claim 20, wherein said tension frames consist essentiallyof a carbon fiber compound.
 22. The clamping device according to claim21, wherein said carbon fiber compound comprises an intermodular fiberof a volume portion of fibers of approximately 50-65% in an epoxy resinmatrix.
 23. The clamping device according to claim 13 configured for theproduction of plastic, metal, ceramic, or glass parts with the formingtool.
 24. A device for producing metal parts by hydroforming, at leastcomprising a parted forming tool and a clamping device according toclaim
 13. 25. A component part for a clamping device of an apparatus forproducing plastic, metal, ceramic, or glass parts by forming processeswith a closed forming tool, the component part comprising: a tensionloop having at least one tension frame with a closed contour, saidtension frame having two mutually opposite segments each formed with atleast one bearing surface and spaced apart at a spacing distance forreceiving a forming tool therebetween, and a material of said tensionframe primarily consisting of a reinforced compound; said bearingsurface corresponding with a bearing surface above or beneath the tooland/or on a surface of the tool, one or a plurality of clamping forcesof a total of at least 1 MN being applied to the component and actingbetween said bearing surface of said tension loop and at least onesurface located underneath or above the tool, the clamping force orclamping forces acting on said tension loop such that a resulting forceintroduction line runs substantially parallel and in a plane that doesnot substantially differ from a plane parting said tension loop in acenterline axial direction.
 26. The component part according to claim25, wherein said tension loop is connected to at least one articulatedjoint enabling said tension loop to pivot towards the tool.
 27. Thecomponent part according to claim 25, wherein said tension loop ismounted for shifting towards the tool.